Friends and family of two Queensland couples on a missing China-bound Malaysia Airlines jet are praying for a miracle.

Catherine and Robert Lawton, from Springfield Lakes, and friends Mary and Rodney Burrows, from Middle Park, are among 239 people on board flight MH370, which slipped off radar screens between Malaysia’s east coast and southern Vietnam on Saturday.

Two other Australians on the flight, Li Yuan and Gu Naijun, are from Sydney.

Vietnam said its search planes had spotted oil slicks in the sea near where the Boeing 777 mysteriously vanished, and ships had been sent to the area.

In Queensland, the Lawtons are being described as passionate travellers who doted on their three daughters and two grandchildren.

“Bobby’s a very good father, such a good person,” Robert Lawton’s brother David Lawton told News Corp.

His wife Rhonda said the couple, in their mid-50s, had planned the trip to China with their good friends the Burrowses.

“Cathy’s last comment on Facebook was ‘Off to China’,” she said.

In Middle Park, neighbours Mandy Watt and Don Stokes said the Burrowses were hard-working parents of two adult daughters and a son, and had moved house just a fortnight ago.

“The kids had moved on ... they’re all successful, all happy. This was their time,” Watt told News Corp. “I hate to use the cliche but they were soulmates.”

Stokes said Rodney Burrows planned the overseas trip after being made redundant last year.

Perth-based Paul Weeks was one of two New Zealanders on the passenger list

Mr Weeks left Christchurch for Perth in 2011 with his wife, Danica, and two young children after the earthquakes in search of a better life, the Sydney Morning Herald reported.

The 38-year-old was en route to Mongolia for his new job with Transwest Mongolia.

The Prime Minister, Tony Abbott, said Australians’ thoughts were with the families of those on the missing jet.

Abbott on Sunday described the tragedy as a “horrible, horrible business”.

“Our thoughts and prayers are with the passengers and their families on that ill-fated aircraft, particularly to the six Australian passengers and their families, that have now been confirmed to be on board,” he said in Adelaide.

“We’re looking at ways in which we can help with the search and recovery operation.”

The opposition leader, Bill Shorten, echoed Abbott’s comments.

“I believe the Australian nation’s thoughts go out to the families of those Australians and New Zealanders that are on this plane, and indeed the families of everyone,” he said in Melbourne.

Australian authorities said they “feared the worst” for all on board the jet.

“Consular officials are currently in touch with Malaysian Airlines and with the families of the missing Australian passengers,” Brett Mason, parliamentary secretary to the minister for foreign affairs, said.

“At the moment there is no clarity as to what has occurred.

“But can I just add that the families of the ... missing Australian passengers must be desperately concerned and the thoughts of the Australian government and I’m sure all Australians go out to them at the moment.”